JP3709965B2

JP3709965B2 - Cylindrical lithium ion battery

Info

Publication number: JP3709965B2
Application number: JP07932099A
Authority: JP
Inventors: 賢治中井; 健介弘中
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Resonac Corp
Priority date: 1999-03-24
Filing date: 1999-03-24
Publication date: 2005-10-26
Anticipated expiration: 2019-03-24
Also published as: JP2000277153A

Description

【０００１】
【発明の属する技術分野】
本発明は円筒形リチウムイオン電池に係り、特に円筒形電池缶内に電極捲回群と該電極捲回群から各極端子へ接続するための接続部とを内蔵した円筒形リチウムイオン電池に関する。
【０００２】
【従来の技術】
リチウムイオン二次電池は、高エネルギー密度であるメリットを活かして、主にＶＴＲカメラやノートパソコン、携帯電話等のポータブル機器の電源に使用されている。円筒形リチウムイオン二次電池の内部は、正極及び負極の両電極が共に活物質が金属箔に塗着された帯状であり、セパレータを挟んでこれら両電極が直接接触しないように断面が渦巻状に捲回され、捲回群が形成された捲回式の構造とされている。そして、この捲回群が円筒形の電池缶内に収納され、電解液注液後、封口される。一般的な円筒形リチウムイオン二次電池の外形寸法は、１８６５０型と呼ばれる、直径１８ｍｍ、高さ６５ｍｍであり、小型民生用リチウムイオン電池として広く普及している。
【０００３】
一方、自動車産業界においては環境問題に対応すべく、排出ガスのない、動力源を完全に電池のみとした電気自動車の開発や内燃機関エンジンと電池との両方を動力源とするハイブリッド（電気）自動車の開発が加速され、一部実用段階に到達している。電気自動車の電源となる二次電池には当然高出力、高エネルギーが得られる特性が要求され、この要求を満足する二次電池としてリチウムイオン電池が注目されている。
【０００４】
しかしながら、高エネルギー密度のリチウムイオン二次電池とはいえ、電気自動車に使用する場合の大電流放電、大電流充電に耐え得るためには、電極構造のみならず、電極から電池端子への集電構造にも工夫が必要となる。例えば、特開平第８−１１５７４４号公報、特開平第９−５５２１３号公報、特開平第９−９２２３８号公報、特開平第９−９２２４１号公報、特開平第９−９２３３５号公報には、電極の集電体である金属箔を活物質層から延出させ、そのまま、又は短冊状に加工して集電リング等の接続部に溶接等により接続して、一旦接続部を介して電池端子へと導くリード接続方式を採用し、大電流放電、大電流充電時の電圧降下（ｉＲドロップ）を低減させる技術が提案されている。これらの公報にも開示されているように、大電流放電、大電流充電時の電圧降下を低減させるためには、円筒形リチウムイオン電池内にリード接続部を収納するためのスペースが必要となる。
【０００５】
ところで、電池を電気自動車に搭載するにあたっては、電気自動車ユーザーの多様な要望に応えるために、車体設計、特に電池のパッケージングに自由度を持たせることが好ましい。そのためには、搭載電池の占める空間体積を最小にする必要があり、その最も有効な手段は電池の体積あたりのエネルギー密度（Ｗｈ／ｌ）を最大にすることである、といわれている。すなわち、電気自動車に搭載される電池は、通常複数の単電池を並列、直列に接続されてモジュールを形成しているが、単電池の体積あたりのエネルギー密度を大きくすることが、モジュールサイズの低減には効果的である。
【０００６】
【発明が解決しようとする課題】
しかしながら、体積エネルギー密度を大きくしても、電池の直径Ｄ／長さＬの比によっては、集電体自体の電圧降下や集電体端部の接続部への接続状態から生ずる電圧降下のために、電池単位体積あたりの出力が低下する、という問題点が生ずる。
【０００７】
本発明は上記事実に鑑み、大電流放電が可能でかつ電池単位体積あたりの効率が高い円筒形リチウムイオン電池を得ることを課題とする。
【０００８】
【課題を解決するための手段】
本発明は上記課題を解決するために、円筒形有底電池缶内に電極捲回群と該電極捲回群から各極端子へ接続するための正極接続部及び負極接続部とを内蔵し、前記電池缶の上部に絶縁性ガスケットを介して上蓋が固定された電気自動車用の円筒形リチウムイオン電池において、前記電極捲回群は、正極集電体の両面に正極活物質が塗布された帯状の正極板と負極集電体の両面に負極活物質が塗布された帯状の負極板とが帯状のセパレータを介して断面渦巻状に捲回されたものであり、前記正極接続部は前記電極捲回群の上端に正極集電リングを配置して該正極集電リングの周縁に前記正極集電体の上端部が溶接され、前記負極接続部は前記電極捲回群の下端に負極集電リングを配置して該負極集電リングの周縁に前記負極集電体の下端部が溶接されたものであり、前記正極集電リングは前記上蓋に接続され、前記負極集電リングは前記電池缶に接続されており、前記電池の満充電状態からの放電電流値と前記電池所定の放電終止電圧値との積を前記電池の体積で除した単位体積あたりの出力が最大となるように、該電池の直径／高さの比を０．３１乃至０．３８の範囲に定めたことを特徴とする。
【０００９】
本発明の発明者は、円筒形リチウムイオン電池では、電池の直径／長さの比が所定値より大きいと、電池体積に対して接続部の占める割合が大きくなるので、エネルギー密度が低下し、一方、電池の直径／長さの比が所定値より小さいと、集電体から延出された延出部を接続部へ溶接することが困難となり電圧降下を招き、また同時に、集電体自体の長さのために電圧降下を生ずることを知見すると共に、必ずしもエネルギー密度が大きい電池が単位体積あたりの出力が大きくなるとは限らないことも見出した。
【００１０】
本発明では、円筒形有底電池缶内に電極捲回群と該電極捲回群から各極端子へ接続するための正極接続部及び負極接続部とを内蔵し、電池缶の上部に絶縁性ガスケットを介して上蓋が固定された電気自動車用の円筒形リチウムイオン電池において、電極捲回群を、正極集電体の両面に正極活物質が塗布された帯状の正極板と負極集電体の両面に負極活物質が塗布された帯状の負極板とが帯状のセパレータを介して断面渦巻状に捲回し、正極接続部を電極捲回群の上端に正極集電リングを配置して該正極集電リングの周縁に正極集電体の上端部を溶接し、負極接続部を電極捲回群の下端に負極集電リングを配置して該負極集電リングの周縁に負極集電体の下端部を溶接し、正極集電リングを上蓋に接続し、負極集電リングを電池缶に接続して構成したので、大電流放電が可能であると共に、電池の満充電状態からの放電電流値と前記電池所定の放電終止電圧値との積を前記電池の体積で除した単位体積あたりの出力が最大となるように、電池の直径／高さの比を定めることにより、電池の体積あたりの効率を向上させた。電池単位体積あたりの出力が最大となるような電池の直径／高さの比は０．３１〜０．３８である。
【００１１】
【発明の実施の形態】
以下、図面を参照して本発明を適用した円筒形リチウムイオン二次電池の実施の形態について説明する。
【００１２】
（構成）
図１に示すように、本実施形態の円筒形リチウムイオン二次電池は、その中心部に円筒状の巻き芯１７を備えている。この巻き芯１７の周囲には、帯状の正極板及び負極板が厚さ４０μｍの微多孔性のポリエチレンフィルムからなる帯状のセパレータＷ５を介して電池円筒断面渦巻状に捲回された捲回群Ｗが配置されている。
【００１３】
正極板は、厚さ２０μｍのアルミニウム箔の正極集電体Ｗ１と正極集電体Ｗ１の両面に塗布された正極活物質層Ｗ２とで構成されている。この正極活物質層Ｗ２は、正極活物質のリチウムマンガン複合酸化物となるマンガン酸リチウムと、導電助剤となるグラファイトと、バインダー（結着剤）となるポリフッ化ビニリデン（ＰＶＤＦ）と、を構成物質とする層である。なお、後述する電解液の注入前の正極板の厚さは９８＋−２μｍであり、正極活物質層Ｗ２の密度は２．６５ｇ／ｃｍ^３である。
【００１４】
一方、負極板は、厚さ１０μｍの銅箔の負極集電体Ｗ３と負極集電体Ｗ３の両面に塗布された負極活物質層Ｗ４とで構成されている。負極活物質層Ｗ４は、リチウムイオンを電極反応種とし充電、放電に伴いリチウムイオンを吸蔵、放出する負極活物質となる非黒鉛炭素と、バインダーとなるＰＶＤＦと、を構成物質とする層である。なお、後述する電解液の注入前の負極板の厚さは６０＋−２μｍであり、負極活物質層Ｗ４の密度は１．０２ｇ／ｃｍ^３である。
【００１５】
捲回群Ｗの上部には正極集電体Ｗ１からの電位を集電するためのリング状の正極集電リング１０が配置され、正極集電リング１０は正極集電リング１０を支持する正極集電リング支え８を介して巻き芯１７の上端部に固定されている。
【００１６】
この正極集電リング１０の周縁には、正極活物質層Ｗ２の上部端側から延出された正極集電体Ｗ１の上端部が溶接されている。正極集電リング１０上面には、正極集電リング１０で集電された電位を正極端子まで導くための正極リード板Ｂ１３の一端が溶接されており、正極リード板Ｂ１３の他端は自由端とされている。
【００１７】
正極集電リング１０の上部には、上蓋キャップ１、上蓋ケース２、安全弁３及び弁押さえ４、で構成された上蓋が配置されている。上蓋は、絶縁性のガスケット５を介して電池缶１６上部にかしめられて固定されている。
【００１８】
正極集電リング１０の周縁上部には捲回群Ｗを固定するための正極集電リングスペーサ６が上蓋ケース２の周縁下部に当接して固定されている。上蓋ケース２の中央下部には正極リード板Ａ１２の一端が溶接されている。正極リード板Ａ１２の他端は自由端とされ、正極リード板Ａ１２及び正極リード板Ｂ１３の自由端同士は溶接により接合されている。
【００１９】
一方、捲回群Ｗの下部には負極集電体Ｗ３からの電位を集電するためのリング状の負極集電リング１１が配置されており、負極集電リング１１は負極集電リング１１を支持する負極集電リング支え９を介して巻き芯１７の下端部に固定されている。この負極集電リング１１の周縁には、負極活物質層Ｗ４の下部端側から延出された負極集電体Ｗ３の下端部が溶接されている。
【００２０】
負極集電リング１１の下部側は負極集電リング１１で集電された電位を負極端子まで導くための断面逆ハット状の負極リード板１４のハット開口周縁部が溶接されており、負極リード板１４のハット先端平面部は電池缶１６に溶接されている。負極集電リング１１と電池缶１６との間には、捲回群Ｗを固定するための負極集電リングスペーサ７が固定されている。
【００２１】
電池缶１６内には、体積比にして３０：５０：２０のエチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）とジエチルカーボネート（ＤＥＣ）の混合溶媒に、１モル濃度となるように６フッ化リン酸リチウム（ＬｉＰＦ_６）が溶解された図示しない電解液５０ｍｌが注入されている。なお、図１中参照番号１５は正極側と負極側とを絶縁する絶縁フィルムである。
【００２２】
（作製方法）
次に、本実施形態の円筒形リチウムイオン二次電池の作製方法について説明する。
【００２３】
正極板を作製するには、マンガン酸リチウム（平均粒径約２０μｍ）とグラファイト（平均粒径約５μｍ）とＰＶＤＦとをそれぞれ重量比８０：１０：１０の割合で十分混合し、そこへ分散媒となるＮ−メチル−２−ピロリドン（ＮＭＰ）を適量加え、十分に混練、分散させ、スラリー状とした正極活物質を得る。この混練物をロールからロールへの転写（ロール・ツー・ロール転写）により正極集電体Ｗ１を挟んだ正極活物質層Ｗ２の両面が同じ厚さとなるように塗着し、乾燥させた後、プレスにより所定厚さとなるまで正極活物質層Ｗ２の両面を圧縮し、裁断して帯状の正極板を得る。
【００２４】
負極板を作製するには、平均粒径２０μｍの非黒鉛炭素とＰＶＤＦとを重量比９０：１０で十分混合し、そこへ分散媒となるＮＭＰを適量加え、十分に混練、分散させ、スラリー状とした負極活物質を得る。この混練物をロール・ツー・ロール転写により負極集電体Ｗ３を挟んだ負極活物質層Ｗ４の両面に同じ厚さとなるように塗着し、乾燥させた後、プレスにより所定厚さになるまで負極活物質層Ｗ４の両面を圧縮し、裁断して帯状の負極板を得る。なお、本実施形態では非黒鉛炭素として呉羽化学工業（株）製の商品名カーボトロンＰを用いた。
【００２５】
得られた帯状の正極板及び負極板の間にこれら両極板が直接接触しないようにセパレータＷ５を挟んで捲回することにより捲回群Ｗを得る。
【００２６】
捲回群Ｗの両端に正極集電リング１０、負極集電リング１１を配置して、正極集電リング１０、負極集電リング１１の周縁にそれぞれ正極集電体Ｗ１、負極集電体Ｗ３から延出された上端部、下端部を溶接する。正極集電リング１０、負極集電リング１１をそれぞれ正極集電リング支え８、負極集電リング支え９を介して巻き芯１７の端部に固定する。
【００２７】
この集電リング付き捲回群Ｗを、負極集電リング１１側が底側になるように電池缶１６に挿入し、負極集電リング１１に予め溶接させておいた負極リード板１４のハット先端平面部を電池缶１６に溶接する。その際、負極集電リング１１と電池缶１６との間には、捲回群Ｗを固定するための負極集電リングスペーサ７を配置する。また、正極集電リング１０上面には、正極リード板Ｂ１３を予め溶接しておく。
【００２８】
一方、上蓋を別途作製し、上蓋ケース２には、正極リード板Ａ１２を溶接によって取り付けておく。正極集電リング１０の周縁上部に正極集電リングスペーサ６を配置する。正極リード板Ａ１２及び正極リード板Ｂ１３の自由端同士を溶接し、上蓋と集電リング付き捲回群とを接続する。この状態で電解液を電池缶１６内に注入する。その後、絶縁性のガスケット５を介して上蓋を電池缶１６上部に配置、かしめることにより本実施形態の円筒形リチウムイオン二次電池が完成される。
【００２９】
本実施形態では、下表１に示すように、実施例１〜３及びこれら実施例の効果を確認するための比較例１〜９の種々の直径、高さを有する電池を作製した。
【００３０】
【表１】

【００３１】
なお、電池缶１６の厚さは０．５ｍｍであり、電池缶１６の内径と電解液注入前の捲回群Ｗの直径との間には、捲回群Ｗを電池缶１６内に収容しやすいように、両側あわせて１ｍｍの隙間が設けられている。この隙間は電解液の注入により捲回群Ｗが膨潤して埋められる。また、これらの電池の捲回群Ｗの端部から各極端子までの接続部に必要な空間として、正極側、負極側あわせて２５ｍｍとした（図１のＡ＋Ｂ＝２５ｍｍ）。また、これらの電池の定格容量を６．２Ａｈとした。
【００３２】
（測定／評価）
次に、このようにして完成した実施例１〜３及び比較例１〜９の電池を２５＋−２℃の雰囲気温度で、４．２Ｖ定電圧、制限電流５Ａ、３時間充電し、満充電状態として次の測定１及び測定２の測定を行った。
【００３３】
[測定１] 満充電状態の電池を１Ａ定電流、放電終止電圧２．７Ｖ、２５＋−２℃で放電し、放電容量を確認した。
【００３４】
[測定２] 満充電状態の電池を１０Ａ、３０Ａ、９０Ａの定電流、２５＋−２°Ｃでそれぞれ放電し、各放電開始後５秒目の電池電圧値を各電流値に対してプロットした直線の傾きの電池所定の放電終止電圧２．７Ｖと交差するところの電流値とこの２．７Ｖの積として出力（Ｗ）を求め、電池の体積あたりの出力（以下、出力密度（Ｗ／ｌ）という。）を算出した。
【００３５】
[測定１の結果] 測定１により測定した測定結果を表２に示す。
【００３６】
【表２】

【００３７】
表２に示すように、実施例１〜３及び比較例１〜９の各電池はすべて、容量６．２Ａｈ、平均電圧４．２Ｖ、エネルギー２３．２５Ｗｈを有することを確認することができた。表２から、比較例５〜９の電池、すなわち、高さＬに対する直径Ｄの比（以下、Ｄ／Ｌ比という。）が０．３未満の電池（表１も参照）のエネルギー密度は、実施例１〜３の電池のエネルギー密度より大きいことが分かる。なお、表２において、電池体積（ｌ）は表１の高さＬ及び直径Ｄから求めたものである。
【００３８】
[測定２の結果] 測定２により測定した測定結果を表３に示す。
【００３９】
【表３】

【００４０】
図２は、縦軸に表１に示したＤ／Ｌ比をとり、縦軸に表３に示した出力密度（Ｗ／ｌ）をとったものである。図２に示すように、出力密度（Ｗ／ｌ）は、Ｄ／Ｌ比が約０．３５のところで最大となることがわかる。従って、電池体積あたりの出力が大きく、換言すれば大電流放電が可能な電池を得るには、Ｄ／Ｌ比が、０．３〜０．４の範囲にあることが必要である。
【００４１】
Ｄ／Ｌ比が約０．４を越えると出力密度が低下するのは、電池内に占める接続部の体積（図１のＡ部及びＢ部の体積）の割合が増加するためである。逆に、Ｄ／Ｌ比が０．３未満でも出力密度が低下するのは、電池の直径Ｄが小さくなるので正極集電リング１０、負極集電リング１１の直径が制約されることから大電流放電時の電圧降下を招くと共に、正極集電体Ｗ１及び負極集電体Ｗ３の長手方向と直交する方向の長さ（図１のＣ）が長くなるので、電子伝導抵抗が大きくなり、大電流放電時の電圧降下が大きくなるからである。
【００４２】
このように、円筒形リチウムイオン二次電池の形状が自由に選択できる場合に、エネルギー密度を大きくすることは好ましいが、エネルギー密度が大きい電池が必ずしも出力密度が大きいとは限らず、Ｄ／Ｌ比が０．３〜０．４の範囲にある電池が単位体積あたり利用しうる出力が最大となる。
【００４３】
なお、本実施形態では正極集電体Ｗ１、負極集電体Ｗ２をそのまま延出させ上部端、下部端を正極集電リング１０、負極集電リング１１に溶接したが、Ｄ／Ｌ比が０．３〜０．４より小さい場合に上述した公報にも記載されているようにこれらの延出部を短冊状に加工したときでも、延出部の一部が欠落しているので正極集電リング１０、負極集電リング１１への溶接は若干容易になるが、延出部が欠落していることにより全面が正極集電リング１０、負極集電リング１１に溶接されないので、大電流放電時に電圧降下を招くことは明らかである。
【００４４】
また、本発明は上記実施形態で説明した直径Ｄ及び高さＬに限定されるものではなく、正極合剤中の導電剤、負極活物質中の炭素材等の物質や製造方法に限定されるものでもない。
【００４５】
【発明の効果】
以上説明したように本発明によれば、円筒形有底電池缶内に電極捲回群と該電極捲回群から各極端子へ接続するための正極接続部及び負極接続部とを内蔵し、電池缶の上部に絶縁性ガスケットを介して上蓋が固定された電気自動車用の円筒形リチウムイオン電池において、電極捲回群を、正極集電体の両面に正極活物質が塗布された帯状の正極板と負極集電体の両面に負極活物質が塗布された帯状の負極板とが帯状のセパレータを介して断面渦巻状に捲回し、正極接続部を電極捲回群の上端に正極集電リングを配置して該正極集電リングの周縁に正極集電体の上端部を溶接し、負極接続部を電極捲回群の下端に負極集電リングを配置して該負極集電リングの周縁に負極集電体の下端部を溶接し、正極集電リングを上蓋に接続し、負極集電リングを電池缶に接続して構成したので、大電流放電が可能であると共に、電池の満充電状態からの放電電流値と前記電池所定の放電終止電圧値との積を前記電池の体積で除した単位体積あたりの出力が最大となるように、電池の直径／高さの比を０．３１乃至０．３８の範囲に定めたので、電池の体積あたりの効率を向上させることができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用される円筒形リチウムイオン二次電池の断面図である。
【図２】本発明が適用される実施例及び実施例の効果を確認するための比較例の各電池のＤ／Ｌ比を横軸にとり、出力密度を縦軸にとったときの出力密度特性図である。
【符号の説明】
１０正極集電リング（接続部の一部）
１１負極集電リング（接続部の一部）
１２正極リード板Ａ（接続部の一部）
１３正極リード板Ｂ（接続部の一部）
１４負極リード板（接続部の一部）
１６電池缶
Ｄ電池の直径
Ｌ電池の長さ
Ｗ捲回群
Ｗ１正極集電体
Ｗ３負極集電体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical lithium ion battery, and more particularly to a cylindrical lithium ion battery in which an electrode winding group and a connection portion for connecting to each electrode terminal from the electrode winding group are incorporated in a cylindrical battery can.
[0002]
[Prior art]
Lithium ion secondary batteries are mainly used as power sources for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. The inside of the cylindrical lithium ion secondary battery is a strip shape in which both the positive electrode and the negative electrode are coated with an active material on a metal foil, and the cross section is spiral so that these electrodes are not in direct contact across the separator The wound structure is formed by forming a wound group. And this winding group is accommodated in a cylindrical battery can, and it is sealed after electrolyte solution injection. The external dimensions of a general cylindrical lithium ion secondary battery, which is called 18650 type, are 18 mm in diameter and 65 mm in height, and are widely used as small-sized consumer lithium ion batteries.
[0003]
On the other hand, in the automobile industry, in order to respond to environmental problems, the development of an electric vehicle with no exhaust gas and a power source completely made of only a battery, or a hybrid (electric) that uses both an internal combustion engine and a battery as a power source. The development of automobiles has been accelerated, and some have reached the practical stage. Naturally, a secondary battery serving as a power source for an electric vehicle is required to have characteristics capable of obtaining high output and high energy, and a lithium ion battery is attracting attention as a secondary battery that satisfies this requirement.
[0004]
However, even though it is a high-energy density lithium ion secondary battery, in order to withstand large current discharge and large current charge when used in an electric vehicle, not only the electrode structure but also the current collection from the electrode to the battery terminal The structure also needs to be devised. For example, JP-A-8-115744, JP-A-9-55213, JP-A-9-92238, JP-A-9-92241, and JP-A-9-92335 include electrodes. The metal foil, which is a current collector, is extended from the active material layer, processed as it is or into a strip shape, and connected to a connection part such as a current collection ring by welding or the like, and once to the battery terminal via the connection part A technique for reducing the voltage drop (iR drop) during large current discharge and large current charge has been proposed. As disclosed in these publications, in order to reduce the voltage drop during large current discharge and large current charge, a space for accommodating the lead connection portion in the cylindrical lithium ion battery is required. .
[0005]
By the way, when mounting a battery on an electric vehicle, it is preferable to provide flexibility in vehicle body design, in particular, battery packaging, in order to meet various needs of electric vehicle users. For this purpose, it is necessary to minimize the space volume occupied by the on-board battery, and it is said that the most effective means is to maximize the energy density (Wh / l) per volume of the battery. In other words, a battery mounted in an electric vehicle is usually formed by connecting a plurality of single cells in parallel and in series to form a module. However, increasing the energy density per unit cell volume reduces the module size. It is effective.
[0006]
[Problems to be solved by the invention]
However, even if the volumetric energy density is increased, depending on the ratio of the diameter D / length L of the battery, the voltage drop caused by the voltage drop of the current collector itself or the connection state of the current collector end to the connection part may occur. In addition, there arises a problem that the output per unit volume of the battery is lowered.
[0007]
In view of the above facts, an object of the present invention is to obtain a cylindrical lithium ion battery capable of discharging a large current and having high efficiency per unit volume of the battery.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention incorporates an electrode winding group and a positive electrode connecting portion and a negative electrode connecting portion for connecting to each electrode terminal from the electrode winding group in a cylindrical bottomed battery can, In the cylindrical lithium ion battery for an electric vehicle in which an upper lid is fixed to the upper part of the battery can via an insulating gasket, the electrode winding group is a belt-like shape in which a positive electrode active material is applied to both surfaces of a positive electrode current collector positive electrode plate and negative electrode plate of the belt-shaped negative electrode active material is coated on both surfaces of the anode current collector via a strip-shaped separator has been wound to cross a spiral shape, and the positive electrode connecting portion before Symbol electrodes the upper end portion of the winding group of the previous SL on the periphery of the positive electrode current collector-ring by placing the positive electrode current collector-ring on end cathode current collector is welded, the negative electrode connecting portion of the electrode winding group lower The negative electrode current collector ring is disposed on the negative electrode current collector ring, and the lower end of the negative electrode current collector is melted around the periphery of the negative electrode current collector ring. Are those that are, the positive electrode collector ring is coupled to the upper cover, the negative electrode collector ring is connected to the battery can, the battery predetermined discharge and the discharge current value from the fully charged state of the battery The battery diameter / height ratio is determined to be in the range of 0.31 to 0.38 so that the output per unit volume obtained by dividing the product of the end voltage value by the volume of the battery is maximized. Features.
[0009]
The inventor of the present invention, in a cylindrical lithium ion battery, if the ratio of the battery diameter / length is larger than a predetermined value, the proportion of the connection portion with respect to the battery volume increases, so the energy density decreases, On the other hand, if the ratio of the diameter / length of the battery is smaller than a predetermined value, it becomes difficult to weld the extended portion extending from the current collector to the connection portion, resulting in a voltage drop, and at the same time, the current collector itself. It has been found that a voltage drop occurs due to the length of the battery, and it has also been found that a battery with a large energy density does not necessarily have a large output per unit volume.
[0010]
In the present invention, an electrode winding group and a positive electrode connecting portion and a negative electrode connecting portion for connecting to each electrode terminal from the electrode winding group are incorporated in a cylindrical bottomed battery can, and an insulating property is formed on the upper portion of the battery can. In a cylindrical lithium ion battery for an electric vehicle having an upper lid fixed via a gasket, an electrode winding group is formed of a strip-like positive electrode plate having a positive electrode active material applied on both sides of a positive electrode current collector and a negative electrode current collector. wound to cross the spiral and the negative electrode plate of the belt-shaped negative electrode active material is coated on both sides via a strip-shaped separator, by placing the positive electrode current collector-ring the positive electrode connecting portion to the upper end of the conductive Gokumeku times group welding the upper end portion of the positive electrode current collector on the periphery of the positive electrode current collector-ring, anode current to the periphery of the negative electrode collector ring by placing a negative electrode collector ring at the lower end of the electrode winding group a negative electrode connecting portion welding the lower end of the collector, to connect the positive electrode collector ring upper lid, configured to connect the negative electrode collector ring to the battery can Therefore, large current discharge is possible, and the output per unit volume obtained by dividing the product of the discharge current value from the fully charged state of the battery and the predetermined discharge end voltage value of the battery by the volume of the battery is maximum. Thus, by determining the battery diameter / height ratio, the efficiency per battery volume was improved. The battery diameter / height ratio is 0.31 to 0.38 so that the output per battery unit volume is maximized.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a cylindrical lithium ion secondary battery to which the present invention is applied will be described with reference to the drawings.
[0012]
(Constitution)
As shown in FIG. 1, the cylindrical lithium ion secondary battery of the present embodiment includes a cylindrical winding core 17 at the center thereof. Around the winding core 17, a wound group W in which a belt-like positive electrode plate and a negative electrode plate are wound in a battery cylindrical cross-section spiral shape through a belt-like separator W 5 made of a microporous polyethylene film having a thickness of 40 μm. Is arranged.
[0013]
The positive electrode plate is composed of a positive electrode current collector W1 of aluminum foil having a thickness of 20 μm and a positive electrode active material layer W2 applied to both surfaces of the positive electrode current collector W1. This positive electrode active material layer W2 is composed of lithium manganate serving as a lithium manganese composite oxide of the positive electrode active material, graphite serving as a conductive aid, and polyvinylidene fluoride (PVDF) serving as a binder (binder). It is a layer used as a substance. In addition, the thickness of the positive electrode plate before injection of the electrolyte solution described later is 98 + −2 μm, and the density of the positive electrode active material layer W2 is 2.65 g / cm ³ .
[0014]
On the other hand, the negative electrode plate is composed of a negative electrode current collector W3 of copper foil having a thickness of 10 μm and a negative electrode active material layer W4 applied to both surfaces of the negative electrode current collector W3. The negative electrode active material layer W4 is a layer having non-graphite carbon serving as a negative electrode active material that absorbs and releases lithium ions accompanying charging and discharging with lithium ion as an electrode reactive species, and PVDF serving as a binder. . In addition, the thickness of the negative electrode plate before injecting the electrolyte solution described later is 60 + -2 μm, and the density of the negative electrode active material layer W4 is 1.02 g / cm ³ .
[0015]
A ring-shaped positive current collecting ring 10 for collecting the electric potential from the positive electrode current collector W 1 is disposed on the upper part of the wound group W. The positive current collecting ring 10 supports the positive current collecting ring 10. It is fixed to the upper end portion of the winding core 17 via the electric ring support 8.
[0016]
The upper end portion of the positive electrode current collector W1 extending from the upper end side of the positive electrode active material layer W2 is welded to the periphery of the positive electrode current collector ring 10. One end of a positive electrode lead plate B13 for guiding the potential collected by the positive electrode current collector ring 10 to the positive electrode terminal is welded to the upper surface of the positive electrode current collector ring 10, and the other end of the positive electrode lead plate B13 is a free end. Has been.
[0017]
An upper lid composed of an upper lid cap 1, an upper lid case 2, a safety valve 3 and a valve presser 4 is disposed on the upper part of the positive electrode current collecting ring 10. The upper lid is caulked and fixed to the upper part of the battery can 16 via an insulating gasket 5.
[0018]
A positive current collector ring spacer 6 for fixing the winding group W is fixed to the upper peripheral edge of the positive current collector ring 10 in contact with the lower peripheral edge of the upper lid case 2. One end of the positive electrode lead plate A12 is welded to the lower center of the upper lid case 2. The other end of the positive electrode lead plate A12 is a free end, and the free ends of the positive electrode lead plate A12 and the positive electrode lead plate B13 are joined together by welding.
[0019]
On the other hand, a ring-shaped negative electrode current collecting ring 11 for collecting the electric potential from the negative electrode current collector W3 is disposed below the wound group W. The negative electrode current collecting ring 11 is connected to the negative electrode current collecting ring 11. It is fixed to the lower end portion of the winding core 17 through a supporting negative electrode current collecting ring support 9. The lower end portion of the negative electrode current collector W3 extending from the lower end side of the negative electrode active material layer W4 is welded to the periphery of the negative electrode current collector ring 11.
[0020]
The lower opening side of the negative electrode current collector ring 11 is welded to the peripheral edge of the hat opening of the negative electrode lead plate 14 having a reverse hat shape for guiding the potential collected by the negative electrode current collector ring 11 to the negative electrode terminal. The flat top portion of the hat 14 is welded to the battery can 16. A negative electrode current collector ring spacer 7 for fixing the wound group W is fixed between the negative electrode current collector ring 11 and the battery can 16.
[0021]
In the battery can 16, phosphorous hexafluoride is mixed in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) at a volume ratio of 30:50:20 so that the molar concentration is 1 mol. 50 ml of an electrolyte solution (not shown) in which lithium acid (LiPF ₆ ) is dissolved is injected. In FIG. 1, reference numeral 15 denotes an insulating film that insulates the positive electrode side and the negative electrode side.
[0022]
(Production method)
Next, a manufacturing method of the cylindrical lithium ion secondary battery of this embodiment will be described.
[0023]
In order to produce the positive electrode plate, lithium manganate (average particle diameter of about 20 μm), graphite (average particle diameter of about 5 μm), and PVDF are sufficiently mixed in a weight ratio of 80:10:10, respectively, and a dispersion medium is mixed therewith. An appropriate amount of N-methyl-2-pyrrolidone (NMP) is added and sufficiently kneaded and dispersed to obtain a positive electrode active material in a slurry state. After this kneaded product was applied so that both surfaces of the positive electrode active material layer W2 having the positive electrode current collector W1 sandwiched by roll-to-roll transfer (roll-to-roll transfer) have the same thickness, and dried, Both sides of the positive electrode active material layer W2 are compressed by pressing until a predetermined thickness is obtained and cut to obtain a belt-like positive electrode plate.
[0024]
In order to produce the negative electrode plate, non-graphite carbon having an average particle size of 20 μm and PVDF are sufficiently mixed at a weight ratio of 90:10, and an appropriate amount of NMP as a dispersion medium is added thereto, and sufficiently kneaded and dispersed. A negative electrode active material was obtained. The kneaded material is applied to both surfaces of the negative electrode active material layer W4 sandwiching the negative electrode current collector W3 by roll-to-roll transfer, dried, and then pressed to a predetermined thickness. Both surfaces of the negative electrode active material layer W4 are compressed and cut to obtain a strip-shaped negative electrode plate. In this embodiment, the trade name Carbotron P manufactured by Kureha Chemical Industry Co., Ltd. was used as non-graphite carbon.
[0025]
A wound group W is obtained by winding with the separator W5 sandwiched between the obtained strip-shaped positive electrode plate and negative electrode plate so that the two electrode plates do not directly contact each other.
[0026]
The positive electrode current collector ring 10 and the negative electrode current collector ring 11 are arranged at both ends of the wound group W, and the positive electrode current collector ring 10 and the negative electrode current collector ring 11 are respectively provided at the peripheral edges from the positive electrode current collector W1 and the negative electrode current collector W3. The extended upper end and lower end are welded. The positive electrode current collecting ring 10 and the negative electrode current collecting ring 11 are fixed to the end of the winding core 17 through the positive electrode current collecting ring support 8 and the negative electrode current collecting ring support 9, respectively.
[0027]
The winding group W with the current collecting ring is inserted into the battery can 16 so that the negative electrode current collecting ring 11 side is the bottom side, and the hat tip plane of the negative electrode lead plate 14 previously welded to the negative electrode current collecting ring 11 is used. The part is welded to the battery can 16. At that time, a negative electrode current collecting ring spacer 7 for fixing the wound group W is disposed between the negative electrode current collecting ring 11 and the battery can 16. Further, a positive electrode lead plate B13 is welded to the upper surface of the positive electrode current collecting ring 10 in advance.
[0028]
On the other hand, an upper lid is prepared separately, and the positive lead plate A12 is attached to the upper lid case 2 by welding. A positive electrode current collector ring spacer 6 is disposed on the periphery of the positive electrode current collector ring 10. The free ends of the positive electrode lead plate A12 and the positive electrode lead plate B13 are welded together to connect the upper lid and the winding group with the current collecting ring. In this state, the electrolytic solution is injected into the battery can 16. Thereafter, the upper lid is disposed on the upper portion of the battery can 16 via the insulating gasket 5 and caulked to complete the cylindrical lithium ion secondary battery of this embodiment.
[0029]
In this embodiment, as shown in Table 1 below, batteries having various diameters and heights of Examples 1 to 3 and Comparative Examples 1 to 9 for confirming the effects of these examples were manufactured.
[0030]
[Table 1]

[0031]
The thickness of the battery can 16 is 0.5 mm, and the wound group W is accommodated in the battery can 16 between the inner diameter of the battery can 16 and the diameter of the wound group W before electrolyte injection. In order to facilitate, a gap of 1 mm is provided on both sides. This gap is filled by swelling the wound group W by injecting the electrolyte. In addition, the space necessary for the connection part from the end of the winding group W of these batteries to each electrode terminal was set to 25 mm for both the positive electrode side and the negative electrode side (A + B = 25 mm in FIG. 1). Moreover, the rated capacity of these batteries was set to 6.2 Ah.
[0032]
(Measurement / Evaluation)
Next, the batteries of Examples 1 to 3 and Comparative Examples 1 to 9 completed in this manner were charged at 4.2 V constant voltage, limit current 5 A for 3 hours at an ambient temperature of 25 + -2 ° C., and fully charged. The following measurement 1 and measurement 2 were performed.
[0033]
[Measurement 1] A fully charged battery was discharged at a constant current of 1 A, a discharge end voltage of 2.7 V, and 25 + -2 ° C, and the discharge capacity was confirmed.
[0034]
[Measurement 2] A fully charged battery was discharged at a constant current of 10A, 30A, and 90A at 25 + -2 ° C, and a battery voltage value at 5 seconds after the start of each discharge was plotted against each current value. The output (W) is obtained as a product of the current value at the intersection of the battery with a predetermined discharge end voltage of 2.7 V and this 2.7 V, and the output per volume of the battery (hereinafter referred to as output density (W / l)) Calculated).
[0035]
[Results of Measurement 1] Table 2 shows the measurement results measured by Measurement 1.
[0036]
[Table 2]

[0037]
As shown in Table 2, it was confirmed that all the batteries of Examples 1 to 3 and Comparative Examples 1 to 9 had a capacity of 6.2 Ah, an average voltage of 4.2 V, and an energy of 23.25 Wh. From Table 2, the energy density of the batteries of Comparative Examples 5 to 9, that is, the ratio of the diameter D to the height L (hereinafter referred to as D / L ratio) is less than 0.3 (see also Table 1). It turns out that it is larger than the energy density of the battery of Examples 1-3. In Table 2, the battery volume (l) is obtained from the height L and the diameter D in Table 1.
[0038]
[Results of Measurement 2] Table 3 shows the measurement results measured by Measurement 2.
[0039]
[Table 3]

[0040]
FIG. 2 shows the D / L ratio shown in Table 1 on the vertical axis and the output density (W / l) shown in Table 3 on the vertical axis. As shown in FIG. 2, it can be seen that the power density (W / l) is maximized when the D / L ratio is about 0.35. Therefore, in order to obtain a battery having a large output per battery volume, in other words, capable of discharging a large current, the D / L ratio needs to be in the range of 0.3 to 0.4.
[0041]
The reason why the output density decreases when the D / L ratio exceeds about 0.4 is that the ratio of the volume of the connection portion (volume of the A portion and B portion in FIG. 1) in the battery increases. On the contrary, the output density decreases even when the D / L ratio is less than 0.3 because the diameter D of the battery is small and the diameters of the positive current collecting ring 10 and the negative current collecting ring 11 are restricted. In addition to incurring a voltage drop during discharge, the length of the positive electrode current collector W1 and the negative electrode current collector W3 in the direction perpendicular to the longitudinal direction (C in FIG. 1) is increased. This is because the voltage drop during discharge increases.
[0042]
As described above, when the shape of the cylindrical lithium ion secondary battery can be freely selected, it is preferable to increase the energy density. However, a battery having a high energy density does not necessarily have a high output density. A battery having a ratio in the range of 0.3 to 0.4 maximizes the output that can be used per unit volume.
[0043]
In this embodiment, the positive electrode current collector W1 and the negative electrode current collector W2 are extended as they are and the upper end and the lower end are welded to the positive electrode current collector ring 10 and the negative electrode current collector ring 11, but the D / L ratio is 0. When the extension is processed into a strip shape as described in the above-mentioned publication when the value is less than 3 to 0.4, a part of the extension is missing. Welding to the ring 10 and the negative electrode current collector ring 11 is slightly easier, but since the entire surface is not welded to the positive electrode current collector ring 10 and the negative electrode current collector ring 11 due to the lack of the extended portion, during large current discharge. It is clear that this causes a voltage drop.
[0044]
Further, the present invention is not limited to the diameter D and the height L described in the above embodiment, but is limited to a material such as a conductive agent in the positive electrode mixture, a carbon material in the negative electrode active material, and a manufacturing method. Not a thing.
[0045]
【The invention's effect】
As described above, according to the present invention, a cylindrical bottomed battery can has a built-in electrode winding group and a positive electrode connecting portion and a negative electrode connecting portion for connecting to each electrode terminal from the electrode winding group, In a cylindrical lithium ion battery for an electric vehicle having an upper lid fixed to the upper part of the battery can via an insulating gasket, the electrode winding group is a band-like positive electrode in which a positive electrode active material is applied on both sides of the positive electrode current collector. wound to cross the spiral plate and negative electrode plate of the belt-shaped negative electrode active material is coated on both surfaces of the anode current collector via a strip-shaped separator, the positive electrode current the positive electrode connecting portion to the upper end of the conductive Gokumeku times group negative electrode current electrodeposition with a-ring is disposed by welding an upper end of the positive electrode current collector on the periphery of the positive electrode current collector-ring, arranged negative electrode collector ring at the lower end of the electrode winding group a negative electrode connecting portion welding the lower end portion of the negative electrode current collector on the periphery of the conductive ring connects the positive electrode collector ring upper lid, the anode current collector phosphorus Is connected to the battery can, so that large current discharge is possible, and the product of the discharge current value from the fully charged state of the battery and the predetermined discharge end voltage value of the battery is divided by the volume of the battery. The battery diameter / height ratio is set in the range of 0.31 to 0.38 so that the output per unit volume is maximized, so that the efficiency per battery volume can be improved. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery to which the present invention is applied.
FIG. 2 is an output density characteristic when the horizontal axis represents the D / L ratio of each battery of the embodiment to which the present invention is applied and the effect of the embodiment is confirmed, and the vertical axis represents the output density. FIG.
[Explanation of symbols]
10 Positive current collector ring (part of connection)
11 Negative current collector ring (part of connection)
12 Positive electrode lead plate A (part of connecting part)
13 Positive electrode lead plate B (part of connecting part)
14 Negative lead plate (part of connection)
16 Battery can D Battery diameter L Battery length W Winding group W1 Positive electrode current collector W3 Negative electrode current collector

Claims

A cylindrical bottomed battery can incorporates an electrode winding group and a positive electrode connecting portion and a negative electrode connecting portion for connecting the electrode winding group to each electrode terminal , and an insulating gasket is provided on the upper portion of the battery can. In the cylindrical lithium ion battery for an electric vehicle with a fixed upper lid, the electrode winding group is formed on both sides of a strip-like positive electrode plate and a negative electrode current collector in which a positive electrode active material is applied on both sides of the positive electrode current collector. and strip-shaped negative electrode plate negative electrode active material is applied via a band-like separator has been wound to cross spiral, the cathode current collector phosphate positive electrode connecting portion in the upper end of the front Symbol electrode winding group the upper end of the front Symbol positive electrode current collector on the periphery of the positive electrode current collector-ring is welded by placing a grayed, the negative electrode connecting portion is negative electrode by placing a negative electrode collector ring at the lower end of the electrode winding group are those lower portions of the negative electrode current collector on the periphery of the current collector ring is welded, the positive electrode current ionization And the negative current collecting ring is connected to the battery can. The product of the discharge current value from the fully charged state of the battery and the predetermined discharge end voltage value of the battery is A cylindrical lithium ion battery characterized in that the ratio of the diameter / height of the battery is set in the range of 0.31 to 0.38 so that the output per unit volume divided by the volume is maximized.

The output per unit volume of the battery is discharged at two or more constant currents that differ from the fully charged state of the battery at room temperature, and the battery voltage value at 5 seconds after the start of each discharge is plotted against each current value. The current value for the predetermined discharge end voltage value of the battery is obtained on a straight line, and the product of the current value and the discharge end voltage value is divided by the volume of the battery. The cylindrical lithium ion battery described.